Even as millions of Americans rally to make donations to the victims of Hurricane Katrina, the Internet is brimming with scams, come-ons and opportunistic pandering related to the relief effort in Louisiana, Mississippi and Alabama. And the scams are more varied and more numerous than in past disasters, according to law enforcement officials and online watchdog groups.

Florida's attorney general has already filed a lawsuit alleging fraud against a man who set up one of the earliest networks of Web sites -- katrinahelp.com, katrinadonations.com and others -- which purported to collect donations for victims of the storm.

In Missouri, a much wider constellation of Internet sites -- parishdonations.com and katrinafamilies.com and others -- displays pictures of the flood-ravaged South and drives traffic to a single site, internetdonations.org, a nonprofit entity with apparent links to anti-Semitic groups.

The registrant of those Web sites was sued by the state of Missouri on Wednesday for violating state fundraising laws and for "omitting the material fact that the ultimate company behind the defendants' Web sites supports white supremacy."

Late Wednesday, the FBI put the number of Web sites claiming to deal in Katrina information and relief -- some legitimate, others not -- at "2,300 and rising." Dozens of suspicious sites claiming links to legitimate charities are being investigated by state and federal authorities. Also under investigation are e-mail spam campaigns using the hurricane as a hook to lure victims to give up credit card numbers to thieves, as well as phony hurricane news sites and e-mails that carry malicious code designed to hijack a victim's computer.

The online scams began to appear within hours of Katrina's passing.

"It was so fast it was amazing," said Audri Lanford, co-director of ScamBusters .org, an Internet clearinghouse for information on various forms of online fraud. "The most interesting thing is the scope," she said. "We do get a very good feel for the quantity of scams that are out there, and there's no question that this is huge compared to the tsunami."

Several anti-virus software companies have warned of e-mail "hurricane news updates" that actually lure users to Web sites capable of infecting computers with a virus that allows hackers to gain control of their machines. And numerous scammers have seeded the Internet with e-mail phishing messages that purport to be from real relief agencies, taking recipients to what appear to be legitimate Web sites, where credit card information is collected from unwitting victims who think they are donating to the cause.

On Sunday, the Internet security company Websense issued an alert regarding a phishing campaign that lured users to a Web site hosted in Brazil and was designed to look like a page operated by the Red Cross. Users who submitted their credit card numbers, expiration dates, and PIN numbers via the Web form were then redirected to the legitimate Red Cross Web site, making the ruse difficult to detect. The security company Sophos warned of a similar phishing campaign on Monday.